近年來，可逆式資訊隱藏吸引了許多目光，其能在嵌入的機密抽取出來後， 無失真的還原原始影像。例如，直方圖位移是可逆式資訊隱藏的主要技術之一。 藉由修改直方圖，資訊可以被藏匿在像素值內，且其偽裝影像確保了高度的視覺 品質。然而，這項技術的嵌密量受到一定的限制。
在本論文中，我們將直方圖位移方法應用在壓縮影像上，來改善嵌密量。所 使用之壓縮演算法為絕對值動量區塊截斷碼 (AMBTC)，一種破壞性壓縮。我們 的方法是近乎可逆的，透過犧牲些許的視覺品質，提供了更大的嵌密量。此外， 我們使用簡單的邏輯操作來加密欲嵌入的訊息，以增強資料安全性。透過金鑰， 使用者能以互斥或運算來產生密文。實驗結果比 Ni 的方法達到了更大的嵌入量， 同時提供了更好的安全性以及良好的偽裝影像之視覺品質。

In the recent years, reversible data hiding scheme has attracted a lot of attention, which is able to recover the original image without distortion after the embedded data is extracted. For example, histogram shifting is one of the major techniques in reversible data hiding. By modifying the histogram, the data can be hidden in a single pixel value, and it still ensures high visual quality in stego image. However, the embedding capacity of this technique is limited.
In this thesis, we improve the capacity by applying histogram shifting method on the compressed image. The compression algorithm to be used is absolute moment block truncation coding (AMBTC), a lossy compression. Our scheme is nearly reversible that offers larger capacity by sacrificing a little visual quality. Furthermore, we encrypt the secret message by a simple logical operation to enhance the data security. With a key given by users, the exclusive-or operation is performed to generate the ciphertext. The experimental results achieve larger embedding capacity than histogram shifting method and also provide with good security and a stego image of good visual quality.

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